Conventionally, slag and dust resulting from steel-making, as well as other industrial waste, etc., are directly discarded in a site for waste disposal because a suitable treatment method has not been found. However, recently, with a view to effectively utilizing resources and reducing waste, utilization of reclaimed resources, that is, recycling of resources, is noted and studied, and the need for establishing a concrete and practical technique for recycling of resources has been pointed out.
Under the above background, reclaiming and utilizing or solidifying and sealing industrial waste, such as fly ash and slag resulting from steel-making, has been studied in various ways. However, a satisfactory method has not yet been developed.
The present inventors, having keenly studied in various ways the method and apparatus, found that it was not always practically easy to obtain reusable molded and solidified materials by melting sulfur at high temperature and mixing it with industrial waste under high temperature, and that there were some problems in the conventional method, as follows, regarding the quality of molded materials solidified by sulfur and operations to make the molded materials.
Namely, products that resulted from solidifying fly ash with sulfur were low in physical strength and sometimes caused cracks. Further, when slag and dust resulting from steel-making were mixed with melted sulfur under high temperature for producing molded materials, in the presence of iron in the slag and dust, irritating sulfurous acid gas was often generated. This adversely affected the molding operation environment, making a deodorizing apparatus indispensable to prevent secondary pollution by the molding operation. In addition to the above, only molded materials that were unsatisfactory in physical strength were obtained, and sometimes the molded materials were cracked.